I've done several.
First thing cut your willow whips in the spring when the bark is slipping and peel them when it is easy. You will find you want smaller in diameter the better. I always cut a bunch and ended up throwing the larger ones away. Best place to get them is along the road a year after they have mowed the brush. You need fast growing but it needs to be somewhere they are reaching for the sun. That makes them long and skinny. Too open and they are shorter and fatter.
Second, an oversized beaver board works good or the end of a line spool to shape them on. I used my nails I tack beaver out with, 12 penny. Nail inside and outside as you bend them in a circle. Might want to mark your board if it doesn't have circles on it. You can nail a bunch up on one board. Put 2nd, 3rd, 4th on the outside of each other. let dry for a few weeks.
Third, it takes two whips to do a hoop. Overlap and attach with several wraps of wire. Bend to approximate sixe of beaver hide and repeat overlap and attach with wire.
Sewing them in you can only render the leather lacing one way. Takes a lot to get it in loose and then you get a lot of it back when you tighten.
Big job but nice when you get done.
